Bangkok is currently investigating possible case of Zika-linked microcephaly in three babies and an unborn fetus, a first of such case in Southeast Asia.

Many countries in Asia recorded increasing numbers of infection from the mosquito-borne Zika virus. Thailand has the highest number of reported cases with 349 since January. The country also disclosed that 25 of these cases are pregnant women.

According to Thailand's Public Health Minister Piyasakol Sakolsatayadorn, authorities need to be careful in their investigation since a confirmed result is a sensitive issue.

The result of the investigation will be released Friday.

It can be recalled that U.S. health officials claimed that Zika infections in pregnant women is the cause of microcephaly in babies. This microcephaly is a birth defect marked by small size of the head, which could lead to serious developmental problems.

As reported by Channel News Asia, Piyasakol added that the three babies were born having small heads while the ultrasound on an unborn fetus also showed that the baby has a small head.

Two of the mothers were diagnosed with Zika when they were still pregnant while the other two were not confirmed to have been infected by the virus.

According to the World Health Organization as published by Washington Post, examining if the baby will be born with microcephaly is difficult to establish since there are no tests to check on that. However, ultrasound in the third trimester can recognize the problem and defect.

The director-general of Thailand's Disease Control Department, Dr. Amnuay Gajeena, mentioned that these four cases were being monitored. He refused to give additional details on the place where the women possibly contracted the virus, but he later stated that it was in Bangkok.

If the result of the investigation is confirmed, the cases of Zika-related microcephaly will be the first in Southeast Asia.